1. Field of the Invention
The invention relates to a shaped charge retention and barrier clip for use in a shaped charge perforating gun.
2. Description of the Prior Art
The perforating guns most commonly used in present-day wireline service operations are typically comprised of an elongated fluid-tight body or so-called "enclosed carrier" which houses one or more shaped explosive charges and the necessary accessories for detonating these charges from the surface. A common type of enclosed carrier has heavy, explosion-resistant walls so that the carrier can be retrieved from the hole.
The shaped charges are usually disposed upon a carrier strip which is inserted into the carrier. Heretofore, the shaped charges have been secured to the carrier strip by means of a brass retainer clip which was frictionally secured to the shaped charge, and then placed in the carrier strip. Additionally, a rubber O-ring has been associated with the shaped charge to provide protection to the interior wall of the carrier upon detonation of the shaped charge, whereby the carrier could be retrieved.
The use of the previously described brass retaining clip and rubber O-ring in association with the shaped charge suffered from the following disadvantages. The use of the brass retainer clip did not provide secure retention of the shaped charge in the carrier strip, since there was a certain degree of wobbling of the shaped charge with respect to the carrier strip once the shaped charge was inserted in the carrier strip. The wobbling of the shaped charge with respect to the strip could cause misalignment between the charge and associated reduced thickness wall portion of the carrier, thereby contributing to decreased performance. Additionally, some force had to be applied to mount the brass retainer clip upon the shaped charge because of the friction fit between those two components. The application of such force could result in the hands of the individual assembling the ring upon the shaped charge to suffer minor cuts and abrasions. The necessity of the friction fit between the shaped charge and the brass retainer ring also required small manufacturing tolerances, whereby the friction fit could be obtained in order to avoid having a shaped charge slide out of the brass retainer ring. Since large-scale wireline service operations require a large number of shaped charges, and related components, over the years the cost of manufacturing the brass retainer clips and the O-rings have risen, as well as the rise in the cost of labor necessary to assemble the shaped charge in the carrier strip. These rising costs have presented an economical problem associated with the prior art brass retainer clip and rubber O-ring used in conjunction with conventional shaped charges and carrier strips.
Accordingly, prior to the development of the present invention, there has been no shaped charge retaining device which: included protection for the interior walls of a retrievable enclosed carrier and provided a secure connection of the shaped charge to the carrier strip without excessive wobble of the shaped charge with respect to the carrier strip; was easy to use in mounting the shaped charge to the carrier strip; and was low in cost to manufacture and use. Therefore, the art has sought an efficient and inexpensive shaped charge retention and barrier clip which is also safe when using it to provide a secure connection of a shaped charge to a carrier strip.